1. Field of the Invention
This invention relates to a solar cell module. More particularly, it relates to a solar cell module that has a high flexibility and superior electrical insulating properties and can prevent peeling.
2. Related Background Art
In recent years, thin-film photovoltaic devices are proposed in a large number. They are typified by, e.g., an amorphous silicon thin-film photovoltaic device comprising a conductive substrate and successively superposingly provided thereon an amorphous silicon semiconductor film and a transparent conductive layer, the former functioning as a photovoltaic device.
Solar cell modules incorporated with such photovoltaic devices are light-weight and high in flexibility, and hence can be used as solar cell modules for which single-crystal silicon solar cells or polycrystalline solar cells can be used with difficulty, e.g., as solar cell modules that are portable and usable in enjoying leisure outdoors, or as solar cell modules that are laminated into metal sheets or the like and usable as roof materials.
Such light-weight and high-flexibility solar cell modules are required to have performances which are different from those of solar cell modules permanently installed. In particular, conventional solar cell modules have a problem of insufficient electrical insulating properties for their output lead-out boxes attached and problems of water exposure and peeling that accompany the attachment of output lead-out boxes. Thus, it has been sought to provide a means for solving these problems. These problems will be detailed below. (Attachment of output lead-out box)
In order to lead out outputs of a solar cell module to the outside, it is common to provide an output lead-out box at the uncovered portion of an output lead-out terminal. Since the solar cell modules permanently installed do not undergo any dynamic force after installation, output lead-out boxes are fastened with adhesives. On the other hand, portable solar cell modules undergo dynamic force, e.g., someone may pull output cables and may walk on output lead-out boxes. Accordingly, the output lead-out box can not have a sufficient mechanical strength if it is only attached with an adhesive. Hence, a method is employed in which the output lead-out box is fastened with bolts and nuts.
When, however, the output lead-out box is fastened with bolts and nuts, concaves or convexes are made on the bottom surface, and hence may cause difficulties such that they catch on something when carried.
Accordingly, one may contemplate to provide projections on the output lead-out box and make holes in the solar cell module so that the projections of the output lead-out box are inserted into the holes to fasten. In this instance, however, water may enter through the holes. Especially when the portions to be fastened are covered with nonwoven fabric in order to ensure the strength at such portions, the water tends to enter along the nonwoven fabric at the holes. Also, portable modules are used, e.g., at the sea or river in many cases. In particular, solar cell modules containing foam can float on water, and are sometimes used in a state where they are floated on water, so that the output lead-out box may, e.g., be swept over by the waves to sink in water. Output lead-out boxes used in such an environment are different from the solar cell modules permanently installed, and are required to have more electrical insulating properties than those used in roof materials.
However, if the nonwoven fabric is removed, the solar cell module has an insufficient strength to cause a problem that, when a force is applied to the output lead-out box, the fastening holes may break to make the output lead-out box tend to be unfastened. In the case of the portable solar cell modules, holes are sometimes made in the solar cell module at its portion having no photovoltaic device so that the solar cell module can be simply fastened with ropes or the like. If the nonwoven fabric is removed from the ends of such a module, the module has an insufficient strength at the holes to cause, e.g., a problem that an external force such as a wind may crack the module from the holes when it is fastened with ropes or the like. (Solar cell modules with foams formed by foaming solid foaming materials in the step of covering)
In solar cell modules having a flexibility, foams are often integrally formed taking account of the buoyancy in water. To form such foams, a solid foaming material may be laminated together with a covering material, which are then foamed in the step of integration to obtain a foamed product. However, a filler constituting the covering material tends to be thinly provided at the edges of the solar cell module. At the edges of a solar cell module making use of nonwoven fabric as a countermeasure therefor, the nonwoven fabric may be provided in a large quantity with respect to the filler, to cause a problem that it tends to peel. The nonwoven fabric also has these problems inherently.